Method and device for forming a roll fold

ABSTRACT

A method for forming a hem by roller hemming may involve providing a first component with a flange portion having an edge and a second component, and producing a hem that connects the first and second components. The hem may be produced by a roller-hemming head that comprises a rolling edge and maneuvers essentially along the flange portion relative to the first component. The object of specifying a method for forming a hem by roller hemming, wherein the formation of wrinkles in the hem flange can be easily reduced or avoided, can be achieved, in the case of a method of the type in question, in that the rolling edge of the roller-hemming head, at least in part, takes up position on, and maneuvers along, the flange portion, and does so at a spacing from the edge of the flange portion.

The present invention relates to a method for forming a hem by roller hemming, wherein a first component and a second component are provided, wherein the first component comprises at least one flange portion comprising an edge, wherein the first component is connected to the second component at least by virtue of a hem being formed, and wherein the hem, at least in part, is produced by means of a roller-hemming head which comprises a rolling edge and maneuvers essentially along the flange portion relative to the first component. The present invention also relates to an apparatus for forming a hem by roller hemming for connecting a first component and a second component, in particular for implementing a method according to the invention, having at least one roller-hemming head, wherein the roller-hemming head comprises a rolling edge, having means for the relative maneuvering of the roller-hemming head along a flange portion of the first component, said flange portion comprising an edge, so that the hem, at least in part, is produced by means of the maneuvering roller-hemming head, and having a control unit for activating the means for the relative maneuvering of the roller-hemming head. Finally, the invention relates to an arrangement made up of a first component and of a second component, wherein the first and the second components, at least in part, are connected by a hem.

Methods of the type in question for forming a hem by roller hemming are used in the prior art for connecting components. Roller hemming here is understood to mean the production of a hem with the aid of a roller-hemming head. It is possible here for a flange region of the first component to be roller hemmed such that said flange region is bent around the peripheral region of the second component. The second component can thus be clamped in on either side between layers of the hemmed first component.

However, it has been found to be problematic that so-called hem-flange wrinkles can form when roller hemming is used for producing hems. The formation of these wrinkles along the hem flange is clearly visible. Along with sometimes poorer attachment of the components, this is particularly problematic for components which remain visible on the finished product, since the appearance is visibly impaired. This is the case, for example, in the production of vehicle-body components. The automotive industry will therefore only accept vehicle-body parts if the hem does not have any visible wrinkles.

The particular problem with the formation of such wrinkles in the flange region during roller hemming is, in addition, that either said hem-flange wrinkles have to be smoothed out by additional method steps, which involves high outlay, or they cannot be reduced to a satisfactory extent retrospectively by follow-up work carried out on the components.

Proceeding from this point, it is an object of the present invention to specify a method and an apparatus for forming a hem by roller hemming, and also to specify an arrangement, wherein the formation of wrinkles in the hem flange can be easily reduced or avoided.

According to a first teaching of the invention, the object is achieved, in the case of a method of the type in question, in that the rolling edge of the roller-hemming head, at least in part, takes up position on, and maneuvers along, the flange portion, and does so at a spacing from the edge of the flange portion.

It has been found that, since the rolling edge of the roller-hemming head on the one hand takes up position on, and maneuvers along, the flange portion, and on the other hand does so at a spacing from the edge of the flange portion, the formation of wrinkles in the hem flange can be reduced, or even avoided, in comparison with conventional methods, in which the flange region is hemmed up to the edge of the flange region. The reduced hem-flange wrinkling means that it is possible to use a hem by roller hemming for connecting a first component to a second component, for example, even when the hem remains visible in the finished component.

The action of the rolling edge of the roller-hemming head on the flange portion can also result in an indentation forming in the flange portion. This is because, since the rolling edge of the roller-hemming head takes up position on, and maneuvers along, the flange portion, and does so at a spacing from the edge of the flange portion, the rolling surface of the roller-hemming head rolls preferably only on a part of the flange portion which is remote from the edge of the flange portion and/or adjoins the rest of the first component. It is therefore just the part which is located between the indentation and the rest of the first component which is hemmed. Conversely, the rolling surface of the roller-hemming head preferably does not roll on an edge portion of the flange portion, said edge portion adjoining the edge of the flange portion. The edge portion, which is located between the edge of the flange portion and the indentation, is essentially not hemmed.

The flange portion can be formed, for example, by an essentially elongate region along the periphery of the first component. It is possible here for the flange portion to project, for example, from the rest of the component, for example essentially at right angles. Such flange portions are particularly suitable for roller-hemming purposes, since the roller-hemming heads can act reliably thereon.

The fact that the roller-hemming head maneuvers along the flange portion relative to the first component can be achieved, for example, in that the roller-hemming head moves, and/or in that the first and second components move. The roller-hemming head preferably maneuvers essentially along the edge of the flange portion relative to the first component. This means that the rolling edge of the roller-hemming head maneuvers essentially at a constant spacing from the edge of the flange portion, which allows straightforward process control.

The fact that the first component is connected to the second component at least by virtue of a rolled hem being formed means that it is also possible for other, or further, connections, for example adhesive-bonding connections, to be provided in addition. It is also additionally possible for further components to be present.

According to one configuration of the method according to the invention, the spacing of the rolling edge of the roller-hemming head from the edge of the flange portion on the flange portion is defined in a component-dependent manner. It has been found that the hem-flange wrinkling can be particularly effectively and reliably reduced or avoided by the spaced positioning and maneuvering if the spacing is adapted in a component-dependent manner. For example, it is possible to define an absolute or relative spacing in relation to the flange height. For example, a preferred spacing can be determined by simulation. If a number of roller-hemming steps are envisaged, the spacing is identical preferably for a number of, preferably for all of, the roller-hemming steps. As result, the rolling edge of the roller-hemming head engages repeatedly in the indentation during the course of the roller-hemming steps.

According to one configuration of the method according to the invention, the rolling edge of the roller-hemming head, at least in part, takes up position on, and maneuvers along, the flange portion at a spacing of approximately 1 mm to 4 mm, preferably approximately 2 mm to 3 mm, from the edge of the flange portion. Although the spacing of the rolling edge of the roller-hemming head from the edge of the flange portion is, in some cases, component-dependent, it has nevertheless been found that hem-flange wrinkling can be reliably avoided in a straightforward manner by such a spacing alone.

As an alternative, it is also possible to use relative information for determining the spacing for the positioning and maneuvering of the rolling edge of the roller-hemming head. For example, the rolling edge of the roller-hemming head can take up position, and maneuver, at approximately 10% to 50% of the height of the flange portion, starting from the edge of the flange portion. Therefore, the part of the flange portion between the edge of the flange portion and the point of attachment of the rolling edge of the roller-hemming head, that is to say the edge portion, is approximately 10% to 50% of the flange portion.

According to a further configuration of the method according to the invention, the positioning angle of the roller-hemming head in relation to the flange portion, at least in part, is approximately 10° to 30°, preferably approximately 20° to 25°. A positioning angle of approximately 10° to 30°, preferably approximately 20° to 25°, while simultaneously providing for an efficient method, satisfactorily reduces or suppresses the hem-flange wrinkling.

The positioning angle is understood to be the angle at which the roller-hemming head is placed in a tilted position. For example, the flange portion is hemmed, or bent over, by this angle during the course of a roller-hemming step. For example, the positioning angle is the angle between the axis of rotation of the roller-hemming head and the flange portion which is to be bent over. If a number of roller-hemming steps are envisaged, the positioning angle is approximately 10°-30°, preferably approximately 20°-25°, at least for one roller-hemming step, preferably for all of the roller-hemming steps.

According to a further configuration of the method according to the invention, the corner radius of the rolling edge of the roller-hemming head tends towards zero. This achieves effective and defined indentation of the flange portion by the rolling edge of the roller-hemming head, and this is beneficial for reducing the hem-flange wrinkling. A corner radius which tends towards zero is understood to mean that said corner radius is negligible in relation to the relevant extents of the roller-hemming head and of the flange portion. For example, the corner radius is smaller than 1 mm, preferably smaller than 0.1 mm. For example, the corner radius is zero. For example, the rolling edge is designed in the form of a rolling/cutting edge.

According to a further configuration of the method according to the invention, the first and/or the second component is a sheet, in particular a composite sheet. Sheets and, in particular, composite sheets tend to undergo hem-flange wrinkling during roller hemming. In the case of such components, it is therefore possible for the method to counteract the flange wrinkling particularly advantageously. This applies, in particular, to sandwich sheets, which comprise two metallic cover layers, for example made of steel, and a plastics-material layer arranged therebetween. Such sheets are used, in particular, in vehicle-body construction on account of their advantageous properties, such as low weight along with a high level of rigidity. Such sheets can advantageously be attached to one another, or to other sheets, by roller hemming. The second sheet here is, for example, an inner sheet and the first sheet is an outer sheet, which is bent around the inner sheet. As an alternative, it is also possible, however, for the first and/or the second component to be a monolithic sheet. It is preferable for the first component to be a sandwich sheet and for the second component to be a monolithic sheet.

According to a further configuration of the method according to the invention, the hem is produced in a number of steps, by way of one or more pre-hemming steps and a definitive-hemming step, by means of one or more roller-hemming heads maneuvering essentially along the flange portion. Implementing the method in a number of steps means that the flange portion is bent over in a stepwise manner, as result of which controlled and reliable hemming takes place, hem-flange wrinkling being reduced or avoided.

For example, it is possible for one, two, three or more pre-hemming steps to take place. These are followed by the definitive-hemming step. The hemming steps can be carried out particularly straightforwardly when a single roller-hemming head is used for the pre-hemming steps and the definitive-hemming step. As an alternative, however, it is also possible to use different roller-hemming heads adapted to the respective hemming step.

For example, a first roller-hemming head can be used for the pre-hemming steps and a second roller-hemming head can be used for the definitive-hemming step. For example, the roller-hemming head is tilted to an increasing extent in relation to the first sheet from one hemming step to the next, and therefore the positioning angle can be kept between 10° and 30° for the hemming steps. For example, the angle between the hemmed part of the flange portion and the rest of the first component is approximately 60° following the first pre-hemming step, approximately 30° following the second pre-hemming step and approximately 10° following the third, and final, pre-hemming step.

According to a further configuration of the method according to the invention, the rolling edge of the roller-hemming head takes up position on, and maneuvers along, the flange portion, and does so at a spacing from the edge of the flange portion, at least for some, preferably for all, of the envisaged pre-hemming steps and the definitive-hemming step. The reduction in hem-flange wrinkling can be improved further by the spacing maintained for a number, or all, of the hemming steps. It is preferably the case, during further hemming steps, that the rolling edge of the respective roller-hemming head therefore takes up position, and maneuvers along, in the region of the indentation produced by the rolling edge of the respective roller-hemming head previously taking up position, and maneuvering, at a spacing from the edge of the flange portion.

According to a further configuration of the method according to the invention, an edge portion produced as a result of the rolling edge of the roller-hemming head taking up position, and maneuvering, at a spacing from the edge of the flange portion is separated off. This can result in a hem which lies flatly against the second component, but has reduced hem-flange wrinkling, if any at all. The edge portion can be separated off efficiently when this operation is carried out during the course of the definitive-hemming step, for example by means of the rolling edge of the appropriate roller-hemming head. As an alternative, it is also possible for this to take place in a separate step following the definitive-hemming step. It is possible here for the edge portion to be, for example, cut off. The separated-off edge portion is preferably then removed, for example by means of an air stream or of a magnet.

As an alternative, it is likewise possible for the edge portion produced by the rolling edge of the roller-hemming head taking up position, and maneuvering, at a spacing from the edge of the flange portion to be roller hemmed over its surface area during the course of the definitive-folding step. This avoids the production of scrap and the necessary removal of the same.

According to a further configuration of the method according to the invention, the hem is in the form of a flat hem or a teardrop hem. Both in the case of flat hemming and of teardrop hemming, the method can easily reduce or avoid the formation of hem-flange wrinkling.

According to a further configuration of the method according to the invention, the first component and the second component are part of a vehicle body. As already outlined in the introduction, the production of vehicle bodies involves the connection of parts by means of roller hemming, wherein the hem may be visible on the finished component. In the case of such vehicle-body parts, the method can easily reduce or avoid the formation of hem-flange wrinkling, so that the appearance is not adversely affected.

According to a second teaching of the invention, the object mentioned in the introduction is achieved, in the case of an apparatus of the type in question, in that the control unit is designed so that it positions the rolling edge of the roller-hemming head on, and maneuvers it along, the flange portion, and does so at a spacing from the edge of the flange portion.

As already explained, it is possible, since the rolling edge of the roller-hemming head on the one hand takes up position, and maneuvers along, the flange portion, and on the other hand does so at a spacing from the edge of the flange portion, for the formation of wrinkles in the hem flange to be reduced, or even avoided, in comparison with apparatuses with control units which are designed so that the flange region is hemmed over its surface area up to the edge of the flange region. The reduced hem-flange wrinkling means that it is possible to use the apparatus for forming a hem in a particularly advantageous manner when the hem remains visible on the finished component.

The means for the relative maneuvering of the roller-hemming head can be realized, for example, by actuators, for example by means of an (industrial) robot. It is also possible for the apparatus to comprise, for example, more than one roller-hemming head, which is advantageous for carrying out a multi-step roller-hemming operation. It is also possible for the apparatus to comprise means for separating off an edge portion. As a further example, it is also possible for the apparatus to comprise means for removing a separated-off edge portion, for example a magnet or a means of generating an air flow.

As far as advantageous configurations of the apparatus and the advantages thereof are concerned, reference is made to the description of the embodiments of the method and the advantages thereof. The intention here is for the previous or following description of method steps according to the preferred embodiments of the method according to the invention also to disclose appropriate means for carrying out the method steps by way of preferred embodiments of the apparatus according to the invention. The intention is likewise for the disclosure of means for carrying out a method step to disclose the appropriate method step.

According to a third teaching of the invention, the object mentioned in the introduction is achieved, in the case of an arrangement of the type in question, in that the hem is produced by roller hemming using a method according to the invention. It is thus possible to provide arrangements with a hem which comprise only reduced hem-flange wrinkling, if any at all. Up until now, such connections produced by roller hemming could not be provided using conventional roller-hemming methods.

The invention will be described in more detail hereinbelow with reference to exemplary embodiments and in conjunction with the drawing, in which:

FIGS. 1-5 show schematic cross-sectional illustrations of a first exemplary embodiment of a method according to the invention at different points in time, and

FIGS. 6a, b show a first and a second exemplary embodiment of an arrangement according to the invention.

FIGS. 1 to 5 show schematic cross-sectional illustrations of a first exemplary embodiment of a method according to the invention at different points in time. The method is implemented here by way of three pre-hemming steps and a definitive-hemming step. However, some other number of method steps is also conceivable in principle. The exemplary embodiment of the method can be implemented here by an exemplary embodiment of an apparatus according to the invention.

FIG. 1 illustrates a first component in the form of a sheet 1, which is a sandwich sheet. The sandwich sheet comprises a first metallic cover layer 1 a, a second metallic cover layer 1 b and a plastics-material layer 1 c arranged therebetween. Also illustrated is a second component in the form of a sheet 2, which is a monolithic sheet. The sheet 1 here constitutes an outer sheet and the sheet 2 constitutes an inner sheet, around the peripheral region of which the sheet 1 can be bent. The sheet 1 comprises a flange portion 4 with an edge 6. The flange portion 4 here is located essentially perpendicularly on the rest of the sheet 1.

FIG. 1 also illustrates how a roller-hemming head 8 with a rolling edge 10 takes up position on the flange portion 4. The corner radius of the rolling edge here tends toward zero. As can be seen, the rolling edge 10 takes up position on the flange portion 4 at a spacing from the edge 6 of the flange portion 4. It is possible for the extent of the spacing A to have been selected, for example, in dependence on the component 1. The spacing A may be approximately 1 mm to 4 mm, preferably 2 mm to 3 mm. In addition, the roller-hemming head takes up position on the flange portion 4 at a positioning angle. The positioning angle is formed by the angle between the axis of rotation 14 and that part 18 of the flange portion 4 which is to be hemmed. The positioning angle is approximately 20° to 30°.

The roller-hemming head 8 then maneuvers along the flange portion, that is to say in a direction perpendicular to the plane of the drawing. The rolling surface 12 here is laid against the flange portion 4 which is to be hemmed. The roller-hemming head rolls on the rolling surface 12 and, in the process, rotates about the axis of rotation 14. As a result, a first roller-hemming step or pre-hemming step is carried out.

The result of the first pre-hemming step is shown in FIG. 2. The rolling edge 10 of the roller-hemming head 8 here has formed an indentation 16 at a spacing A in the flange portion 4. Since the rolling edge 10 of the roller-hemming head 8 has taken up position on, and maneuvered along, the flange portion 4, and has done so at a spacing from the edge 6 of the flange portion 4, during the first pre-hemming step, the rolling surface 12 of the roller-hemming head 8 has rolled only on a part 18 of the flange portion 4 which is remote from the edge 6 of the flange portion 4 and/or adjoins the rest of the first component 1. It is therefore just the part which is located between the indentation 16 and the rest of the first component 1 which is hemmed. Conversely, the rolling surface 12 of the roller-hemming head 8 has not rolled on an edge portion 20 of the flange portion 4, said edge portion adjoining the edge 6 of the flange portion 4. The edge portion 20, which is located between the edge 6 of the flange portion 4 and the indentation 10, has not been hemmed here.

The roller-hemming head 8 is then tilted, so that the positioning angle of the roller-hemming head 8 in relation to the part 18 of the flange portion 4 which is to be hemmed is, once again, approximately 20° to 30°. The rolling edge 10 of the roller-hemming head 8 here once again takes up position on, and moves along, the flange portion 4 in the indentation 16, that is to say at the spacing A from the edge 6 of the flange portion 4, as already described in relation to FIG. 1.

The result of the second roller-hemming or pre-hemming step is illustrated in FIG. 3. The part 18 of the flange portion 4 has been hemmed in accordance with the positioning angle of the roller-hemming head 8 shown in FIG. 2, while the edge portion 20 remains oriented essentially perpendicularly in relation to the rest of the component 1. As illustrated in FIG. 3, and already described in conjunction with FIG. 2, a positioning angle of the roller-hemming head 8 of approximately 20° to 30° in relation to the part 18 of the flange portion 4 which is to be hemmed is set anew and the roller-hemming head 8 takes up position, by way of the rolling edge 10, anew in the region of the indentation 16.

The result of the third roller-hemming or pre-hemming step is illustrated in FIG. 4. The part 18 of the flange portion 4 has been hemmed in accordance with the positioning angle of the roller-hemming head 8 which is shown in FIG. 3, while the edge portion 20 remains oriented essentially perpendicularly in relation to the rest of the component 1. As illustrated in FIG. 4, and already described in conjunction with FIGS. 2 and 3, the positioning angle of the roller-hemming head 8 is corrected anew, the definitive-hemming step then taking place as the fourth roller-hemming step. The part 18 of the flange portion 4 then only has an angle of approximately 10° in relation to the surface of the sheet 2. The axis of rotation 14 of the roller-hemming head then runs essentially parallel to the surface of the rest of the sheets 1 and 2. The positioning angle of the roller-hemming head in relation to the part 18 of the flange portion 4 which is to be hemmed is still approximately 10° here. The roller-hemming head 8 takes up position, by way of the rolling edge 10, anew in the region of the indentation 16 and maneuvers anew along the flange portion 4, exerting pressure on the part 18 of the flange portion 4 in the process.

FIG. 5 shows a cross section of the finished hem 22 following the definitive-hemming step. At the same time as the definitive-hemming step, the rolling edge 10 of the roller-hemming head 8 has separated off the edge portion 20 from the flange portion 4. The edge portion 20 can be removed, for example, by air-suction or magnetic means.

The method illustrated reduces or avoids the formation of wrinkles in the hem flange 4 in comparison with a flange portion which is hemmed by a conventional method, in the case of which the rolling edge 10 takes up position directly on the edge 6, or over the same, and the entire flange portion 4 is therefore hemmed over its full surface area up to the edge 6.

FIGS. 6a and 6b show a first and a second exemplary embodiment of an arrangement according to the invention. The arrangements each comprise a first component 1 and a second component 2, wherein the first component 1 is connected to the second component 2 by a hem 22. The hem 22 here has been produced by roller hemming according to an exemplary embodiment of a method according to the invention, and it has therefore been possible to reduce the hem-flange wrinkling. 

1-13. (canceled)
 14. A method for forming a hem by roller hemming, the method comprising: providing a first component and a second component, wherein the first component comprises a flange portion with an edge; and forming a hem that connects the first and second components at least in part, wherein the hem is produced by a roller-hemming head that comprises a rolling edge, wherein the rolling edge of the roller-hemming head is positioned on the flange portion and maneuvers substantially along the flange portion at a spacing from the edge of the flange portion.
 15. The method of claim 14 further comprising defining the spacing of the rolling edge of the roller-hemming head from the edge of the flange portion in a component-dependent manner.
 16. The method of claim 14 wherein the spacing between the rolling edge of the roller-hemming head and the edge of the flange portion is in a range of 1 mm to 4 mm.
 17. The method of claim 14 wherein the spacing between the rolling edge of the roller-hemming head and the edge of the flange portion is in a range of 2 mm to 3 mm.
 18. The method of claim 14 wherein a positioning angle of the roller-hemming head relative to the flange portion is at least in part in a range of 10° to 30°.
 19. The method of claim 14 wherein a positioning angle of the roller-hemming head relative to the flange portion is at least in part in a range of 20° to 25°.
 20. The method of claim 14 wherein a corner radius of the rolling edge of the roller-hemming head tends toward zero.
 21. The method of claim 14 wherein at least one of the first component or the second component is a sheet.
 22. The method of claim 14 wherein at least one of the first component or the second component is a composite sheet.
 23. The method of claim 14 wherein forming the hem comprises a pre-hemming step and a definitive-hemming step.
 24. The method of claim 23 wherein the roller-hemming head is one of a plurality of roller-hemming heads, wherein the plurality of roller-hemming heads maneuver substantially along the flange portion and perform the pre-hemming and definitive-hemming steps.
 25. The method of claim 23 wherein the rolling edge of the roller-hemming head performs the pre-hemming step and the definitive-hemming step at the spacing from the edge of the flange portion for at least a portion of the pre-hemming step and the definitive-hemming step.
 26. The method of claim 14 further comprising separating off an edge portion produced as a result of the rolling edge of the roller-hemming head being positioned on the flange portion and maneuvering substantially along the flange portion at the spacing from the edge of the flange portion.
 27. The method of claim 14 wherein the hem is configured as a flat hem or a teardrop hem.
 28. The method of claim 14 wherein the first component and the second component are part of a vehicle body.
 29. An apparatus for forming a hem by roller hemming that connects a first component and a second component, the apparatus comprising: a roller-hemming head with a rolling edge; means for relative maneuvering of the roller-hemming head along a flange portion of the first component, wherein the flange portion comprises an edge, wherein the hem is produced at least in part by the means for relative maneuvering of the roller-hemming head; and a control unit for activating the means for relative maneuvering of the roller-hemming head, the control unit configured to cause the means for relative maneuvering of the roller-hemming head to position the rolling edge on and maneuver the rolling edge along the flange portion at a spacing from the edge of the flange portion.
 30. An arrangement comprising a first component and a second component, wherein the first and second components are connected at least in part by a hem, with the first component including a flange, wherein the hem is produced by a roller-hemming head that comprises a rolling edge, wherein the rolling edge of the roller-hemming head is positioned on the flange portion and maneuvers substantially along the flange portion at a spacing from the edge of the flange portion. 